Topic Contents

C-Reactive Protein (CRP)

Test Overview

A
C-reactive protein (CRP) test is a blood test that measures the amount of a
protein called C-reactive protein in your blood.
C-reactive protein measures general levels of
inflammation in your body.

High levels
of CRP are caused by infections and many long-term diseases. But a CRP test
cannot show where the inflammation is located or what is causing it. Other
tests are needed to find the cause and location of the inflammation.

Why It Is Done

A C-reactive protein (CRP) test is done
to:

Check for infection after surgery. CRP levels
normally rise within 2 to 6 hours of surgery and then go down by the third day
after surgery. If CRP levels stay elevated 3 days after surgery, an infection
may be present.

Identify and keep track of infections and diseases
that cause inflammation, such as:

Check to see how well treatment is working, such
as treatment for cancer or for an infection. CRP levels go up quickly and then
become normal quickly if you are responding to treatment measures.

A special type of CRP test, the high-sensitivity CRP test
(hs-CRP), may be done to help find out your risk of a heart attack and stroke. The results can help you and your doctor make decisions about how to lower your risk. The connection between hs-CRP levels and the risk of heart attack and stroke are not understood completely. But high levels may mean that the lining of your arteries are inflamed. This may damage the arteries and raise your risk of a heart attack and stroke.

How To Prepare

There is no special preparation for a
C-reactive protein (CRP) test. You might be asked to not eat or drink for a few hours before the test.

Tell your doctor all of the medicines you are taking because some medicines can affect the results.

Talk to your doctor about any
concerns you have regarding the need for the test, its risks, how it will be
done, or what the results will mean. To help you understand the importance
of this test, fill out the
medical test information form(What is a PDF document?).

How It Is Done

The health professional taking a sample
of your blood will:

Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.

Clean the needle site with
alcohol.

Put the needle into the vein. More than one needle stick
may be needed.

Attach a tube to the needle to fill it with
blood.

Remove the band from your arm when enough blood is
collected.

Put a gauze pad or cotton ball over the needle site as
the needle is removed.

Put pressure on the site and then put on a
bandage.

How It Feels

The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
pinch.

Risks

There is very little chance of a problem from
having a blood sample taken from a vein.

You may get a small bruise at the site. You can
lower the chance of bruising by keeping pressure on the site for several
minutes.

In rare cases, the vein may become swollen after the blood
sample is taken. This problem is called phlebitis. A warm compress can be used
several times a day to treat this.

Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (such as
Coumadin), and other blood-thinning medicines can make bleeding more likely. If
you have bleeding or clotting problems, or if you take blood-thinning medicine,
tell your doctor before your blood sample is taken.

Results

A C-reactive protein (CRP) test is a
blood test that measures the amount of a
protein called C-reactive protein in your
blood.

Normal

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Any condition that results in sudden or severe
inflammation may increase your CRP levels.

Some medicines may
decrease your CRP levels.

Many conditions can change CRP
levels. Your doctor will talk with you about any abnormal results that may be
related to your symptoms and past health.

High-sensitivity C-reactive protein (hs-CRP) levels

High-sensitivity C-reactive protein (hs-CRP) measures very low
amounts of CRP in the blood. This test may help find your risk of heart problems, especially when it is considered along with other risk factors such as cholesterol, age, blood pressure, and smoking. It may be done to
find out if you have an increased chance of having a sudden heart problem, such
as a
heart attack or stroke. But the connection between high CRP
levels and heart disease risk is not understood very well.

What To Think About

C-reactive protein can be found with this test within a few hours of an inflammation response. So a higher-than-normal CRP level shows a current inflammation. The CRP level drops back to normal when the inflammation goes away.

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use.
How this information was developed to help you make better health decisions.